It’s the middle of the snow season so it’s a good time to talk about skiing injuries. Skier’s thumb is an important injury for two main reasons. Firstly, it makes up nearly 10% of ski-related injuries. Secondly, if it is not treated appropriately, it can cause ongoing disability.

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Skier’s thumb is an acute injury to the ulnar collateral ligament (UCL) of the first MCP joint of the hand. It occurs when the thumb is forced into extension and abduction. This can occur if the skier falls and catches the thumb in the snow, and it is also thought to be related to falling with the ski-pole in the hand. Patients present with a typical history, swelling over the thumb MCP joint, and tenderness along the UCL, particularly at its distal insertion.

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The ligament usually tears away from its distal insertion on the base of the proximal phalanx of the thumb. Just like any sprain, there can be mild injuries that result in pain but no laxity, partial tears that lead to minor laxity (these both do well with conservative care), and complete ruptures. Complete ruptures can sometimes be associated with an avulsion fracture.

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Partial (grade 1 and 2) tears usually have less than 20 degrees difference in play when compared to the other thumb, and have a firm end feel. They can be treated with splinting in slight flexion for 6 weeks, and then further protection for at-risk activities for at least another 6 weeks. Check-reign taping (where the thumb is taped loosely to the index finger) works well for return to sport.

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The issue with the complete ruptures and the avulsion fractures is that if the distal end of the ligament is pulled far enough back to pass out from under the extensor hood of the MCP joint, then even if the thumb is splinted in a good position, the end cannot get back to its original point of attachment on the proximal phalanx, and so no amount of rest will result in a stable joint. This is called a Stener lesion. The only way to restore stability in this situation is surgical reattachment. Instability of this joint leads to weakness of the pinch grip and pain.

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If someone sustains this type of injury, getting plain films before stress testing the joint can be useful, because if there is a minimally displaced avulsion fragment, then you have confirmed the diagnosis and ruled out a Stener lesion, and conservative care is reasonable. Stress testing of this joint could displace the avulsion and turn something that would have settled with splinting, into something that will not resolve without surgery. Any subluxation of the base of the proximal phalanx on x-ray requires surgical review as well.

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If the x-rays show a displaced avulsion fragment, then surgery will be necessary. If there is no fracture, and there is gross laxity of the ulnar collateral ligament, then surgical referral should be made. If conservative treatment has been carried out, but there is still grade three laxity, then surgical review will also be necessary.

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